Meiosis: Key Concepts, Stages, and Genetic Variation in Cell Division

What is the primary function of meiosis in sexually reproducing organisms?

To reduce chromosome number from diploid (2n) to haploid (n) and introduce genetic variation.

What is the starting and ending cell type in meiosis?

Starts with 1 diploid cell (2n) and ends with 4 haploid daughter cells (n).

What occurs during Prophase I of meiosis?

Synapsis of homologous chromosomes and crossing over occur, followed by the breakdown of the nuclear membrane.

What happens during Metaphase I of meiosis?

Homologous pairs align at the equator, and independent assortment determines their orientation.

What is the outcome of Anaphase I in meiosis?

Homologues separate and are pulled by spindle fibers, still consisting of 2 chromatids.

What occurs during Telophase I of meiosis?

The nuclear envelope may reform, and cytokinesis may occur, resulting in 2 haploid cells (n).

What is Interkinesis in meiosis?

A short rest period between divisions where no DNA replication occurs and chromosomes still have two chromatids.

What happens during Prophase II of meiosis?

Cells contain one chromosome from each homologous pair.

What occurs during Metaphase II of meiosis?

Chromosomes align at the equator.

What is the outcome of Anaphase II in meiosis?

Centromeres split, sister chromatids separate and move to the poles.

What happens during Telophase II of meiosis?

Nuclear membranes form, and cytokinesis produces 4 haploid daughter cells.

What are the two main mechanisms of genetic variation introduced during meiosis?

Crossing over during Prophase I and independent assortment during Metaphase I.

How does fertilization affect chromosome number?

Fertilization restores the diploid number by combining two haploid gametes (n + n = 2n).

How many divisions occur in meiosis compared to mitosis?

Meiosis has 2 divisions, while mitosis has 1 division.

What types of cells are produced by meiosis compared to mitosis?

Meiosis produces 4 haploid, genetically variable cells; mitosis produces 2 diploid, genetically identical cells.

When does meiosis occur compared to mitosis?

Meiosis occurs during special occasions like gamete formation, while mitosis occurs continually for growth and repair.

In which phase does crossing over occur during meiosis?

Crossing over occurs only in Meiosis I, specifically during Prophase I.